The Effects of Exercise Interventions on Ectopic and Subcutaneous Fat in Patients with Type 2 Diabetes Mellitus: A Systematic Review, Meta-Analysis, and Meta-Regression

Background/Objectives: The aim of the present study was to determine the effects of exercise training on ectopic and subcutaneous fat in patients with type 2 diabetes mellitus (T2DM). Methods: Web of Science, PubMed, and Scopus were searched for original articles published through November 2023 that included exercise versus control interventions on body mass (BM), liver fat percentage, visceral fat area (VFA), subcutaneous fat area (SFA), and intramuscular fat volume or mass (IMF) in patients with T2DM. Weighted mean differences (WMDs) for liver fat and BM, standardized mean differences (SMDs) for VFA, SFA, and IMF, and 95% confidence intervals (95% CIs) were determined using random-effects models. Results: Thirty-six studies comprising 2110 patients with T2DM were included in the present meta-analysis. Exercise training effectively reduced BM [WMD = -2.502 kg, p = 0.001], liver fat% [WMD = -1.559%, p = 0.030], VFA [SMD = -0.510, p = 0.001], and SFA [SMD = -0.413, p = 0.001] in comparison to the control. The IMF [SMD = 0.222, p = 0.118] remained unchanged compared to the controls. Subgroup analyses showed that the type of exercise, duration, and body mass index (BMI) of participants were sources of heterogeneity. Conclusions: The current meta-analysis provides strong evidence that exercise training, particularly aerobic and combined (aerobic and resistance) exercise programs, is effective for reducing BM, VFA, and SFA in patients with T2DM. However, aerobic exercise was more effective for reducing liver fat than combined exercise. The beneficial effects of exercise on VFA and SFA reduction, but not liver fat, are associated with weight loss. These findings highlight the importance of including consistent exercise as a key management component for T2DM and associated ectopic fat deposition, with potential long-term benefits for metabolic health.